October 11, 2013

Irisin Production During Exercise Boosts Brain Health

Exercise is good for nearly every part of your body, including your brain. According to researchers led by Harvard Medical School, a molecule called irisin is produced in the brain during endurance exercise and apparently has neuroprotective effects.

The research team, led by Dr. Bruce Spiegelman of the Dana-Farber Cancer Institute and Harvard Medical School, artificially increased the levels of irisin in the blood to activate genes involved in learning and memory. The research team hopes their results, published online in the journal Cell Metabolism, will be useful for designing drugs that use irisin to guard against neuro-degenerative diseases and improve cognition in the aging population.

Scientists have known for a while that exercise can boost cognitive function and lessen symptoms of neurological diseases like depression, stroke, and Alzheimer's disease. What has been unclear, however, were the mechanisms underlying these effects. Researchers believe that one important player in these mechanisms is a growth factor named brain-derived neurotrophic factor (BDNF).

The researchers conducted experiments using mice, finding that a molecule called FNDC5 and its cleavage product, irisin, are elevated in the brain by endurance exercise and that they increase BDNF expression. In contrast, mice genetically modified to have low irisin levels in the brain had reduced levels of BDNF.

Raising levels of irisin in the circulation, according to the study, caused the molecule to cross the blood-brain barrier, where it increased expression of BDNF and activated genes involved in cognition.

"Our results indicate that FNDC5/irisin has the ability control a very important neuroprotective pathway in the brain," says Dr. Spiegelman.

The team is planning further research to develop a stable form of the irisin protein that can be given to mice by injection and may augment the brain's natural anti-degeneration pathways.